Drive mechanism for feed dogs of sewing machines



R. REEBER July 20, 1965 DRIVE MECHANISM FOR FEED DOGS OF SEWING MACHINES 2 Sheets-Sheet 1 Filed Aug. 8, 1965 Fig.1

INV EN T0 R. 0000 izzaze R. REEBER July 20, 1965 DRIVE MECHANISM FOR FEED DOGS OF SEWING MACHINES 2 Sheets-Sheet 2 Filed Aug. 8, 1963 IN v EN TOR. 0004F51 BY W United States Patent 2 Claims. 61. 112-215 The invention relates to sewing machine mechanism and is particularly concerned with feed dog drive mechanism.

In accordance with the invention certain improvements are introduced in the drive means of feed dogs which provide advantages over such drive means as used heretofore in accordance with the prior art. conventionally in sewing machines the drive means for the feed dog are arranged below the work table or carrier plate. The feeding movement of the feed dog is derived from an eccentric that is arranged on the looper drive shaft and is transmitted to the feed shaft by means of an eccentric bar. The latter presents a stud on which a sliding block is mounted for free rotary movement which slides in an adjustable slotted member. The obliqueness or angle of inclination of said slotted member which determines the extent of the feed movement is adjustable.

In prior art feed dog drive means of this type only a :part of the thrust of the eccentric becomes effective on the feed shaft because of the unfavorable leverage conditions. For great stitch lengths the adjustable slotted member must be positioned in a correspondingly proportioned oblique position, or a curved eccentric must be used. Both of these possibilities are ill-suited for solving the problem solved by the invention, especially in connection with rapidly operating machines. The great obliqueness of the slotted member causes considerable pressure in the sliding track which imparts a resisting moment onto the slotted member and tends to turn the slotted member and thus change the position to which it is set. Curved eccentrics again are subjected to considerably more wear than the curved eccentrics used in rapidly operating machines and result in greater operating disturbances in the machine, such as vibrations.

It is an object of the invention to improve the drive means of the feed dog in :a manner that the thrust of the block becomes fully effective on the feed shaft so that also in connection with great stitch lengths a relatively smaller obliqueness of the position of the adjustable slotted member is required. 'In accordance with the invention this is accomplished in that control means are provided at the free end of the lower drive shaft which is the end remote from the looper and in that the eccentric bar has a bridge member connecting both jaws on which the stud which engages the sliding block is mounted substantially equiaxially with respect to the lower drive shaft.

Further advantages and features of the new feed dog drive means in accordance with the invention will become apparent from the following specification with reference to the accompanying drawings showing an embodiment and in which:

FIG. 1 shows the sewing machine in front View, and

FIG. 2 is a perspective view showing the feed dog drive means on an enlarged scale.

On the base or work plate 1 of the sewing machine a standard 2 is mounted from which the horizontal arm 3 extends which ends in the machine head 4. The arm shaft or drive shaft 5 is journalled in the arm 3 and is connected with the needle bar 7 which carries the thread guiding needle 6 and which is mounted for up and down movement in the head 4. A belt pulley 8 is provided upon arm shaft 5 which by way of belt 9 and the co- Patented July 20, 1965 operating pulley 11 mounted on lower drive shaft 10 transmits the drive movement of arm shaft 5 to the lower drive shaft 10 which is journalled in the machine base 1 and which by way of a pair of gears 12, 13 is connected with the looper drive shaft 15 that carries the looper 14.

A round eccentric 17 is secured to the free end of the lower drive shaft 10 which initiates the feeding movement of the feed dog 16 and which is encompassed by the two jaws 18, 19 of an eccentric bar 20. The eccentric bar 20 is provided with a web or bridge member 21 which connects the two jaws 18, 1-9 and has a stud 22 mounted substantially coaxially with the shaft 10. A sliding block 23 is rotatably mounted on the stud 22 which engages a slotted member for sliding movement. The slotted member is provided with a stud 25 which is journalled in a sleeve 27 mounted in a boss or extension 26 on the base plate and is secured therein in a manner not shown.

The eccentric bar 29 is connected at its free end with a crank 23 that is clamped onto a feed shaft 29 journalled in the base plate 1. The feed shaft 29 has an arm 30 to which a carrying bar 31 is linked which supports the feed dog 16. The carrying bar has a bifurcated end 32 and is connected with a lifting or raising eccentric that is secured to the raising shaft 34 journalled in the base plate. The raising shaft 34 which is driven bylower shaft 10 imp-arts the lifting movements to the feed dog 16. The slot-ted member 24 has an arm 35 to which a draw bar 36 is connected which at its upper end is connected with the arm 37 of a double armed lever 38. The latter is secured to a shaft 40 that is journalled in the standard 2 and has an arm 39 provided with a ball headed end that extends into a groove 41 of a setting disk 42 which is likewise journalled in the standard 2. The groove 41 defines two curved tracks 43 and 44 along its sides which are arranged in such a manner that opposite points along these tracks when cooperating with the ball head 39 of the double armed lever 38 obtain equal feeding lengths for forward and reverse stitching. A spring 45 having one end secured in the standard 2 and the other end to the arm 39 of the double armed lever 38 retains the lever 38 in force transmitting engagement with the curved track 43.

The new driving mechanism for the feed dog operates as follows:

By rotating the setting disk 42 the slotted member 24 is rocked about its stud 25 by way of double armed lever 38 and draw bar 36 and thus is adjusted to a more or less oblique position. As the shaft 10 which drives the looper rotates, the eccentric 17 moves the eccentric lbfil' 20 and thus also the sliding block 23 in the slotted member 24 up and down. The slid-ing block 23 owing to the oblique or inclined position of the slotted member 24 superimposes a movement in horizontal direction in addition to the up and down movement. This horizontal movement is imparted to the crank 28 by way of eccentric bar 20 and is passed on to the feed shaft 29 as a rocking movement, so that the arm 30 imparts the required feeding movement for the material feeding to the feed dog 16. The magnitude of this feeding movement depends on the magnitude of the horizontal movement of the sliding block 23 and thus on the extent of the inclined position of the slot-ted member 24. Owing to the coaxial arrangement of the shaft 10 which drives the looper and of the stud 22 which supports the sliding block 23, the full thrust of the eccentric becomes effective at the sliding block 23 so that even for large stitch lengths only a rel-atively small inclined position of the slotted member 24 is required.

If the adjustable slotted member 24 is turned by rotation of the setting disk 42 to such an extent that it defines a right angle with respect to the eccentric bar 20, then the sliding block 23 does not effect a horizontal movement, so that the magnitude of the rocking movement of the feed shaft 29 is almost zero and consequently the feed dog 16effects practically no feeding movement. If it were desired to obtain theoretically exact zero value for the feeding movement, it would be necessary to employ a grooved member having an arcuate track; in place of the grooved member 24 having a straight track, and

the radius of which is equal to the distance between the with said lower drive shaft to elfect adjustment of said drive means; i I a I a 2. A sewing machine of the type having .a feed dog,

a feed bar drive shaft and a lower drive shaft for driving the l-ooper and drive means connected between said drive shafts for effecting the feeding movement of saidfeed dog,

' said "drive means including afeed bar supporting said feed stud 22 and the connecting point with the crank 28 of the eccentric bar 20. 7

If byyoperating the adjusting lever 46 the slotted member 24 is turned beyond the aforementioned right angle with respect to the eccentric bar 20, then the, sliding block 23 effects a horizontal movement but the swing of Y the feed shaft 29 is in opposite direction, so that'also the feed dog 16 effects a reverse movement. 1- 7 Having now described my invention, with reference to' the embodiment illustrated in the drawings, I do not wish to be limited thereto, but what I desired to protect by Letters-Patent of the United States of America is set forth in the appended claims.- a

-Iclaim: a V

1. A sewing machine of the type" having a feed dog, a feed bar drive shaft and alower drive shaftfordrivin-g the looper and drive means connected between said drive shaftsfor effecting the feeding movement of said feed dog, said drive means including afeed bar supporting said 7 feed dog and operatively con'nectedt-o said feed bar drive shaft, an eccentric bar pivotally connected at one end to said feed bar d-rive'shaft and having two eccentric en gaging jaws at the other end, an eccentric member mount ed on the free end of said lower drive shaft, said eccentric bar having a bridge member. -intermediate said two jaws, said bridge member having a stud extending substantially coaxially with the axis :of said lower drive shaft and a sliding block rotably mounted on said stud, and a slotted member means rotatably mounting said slot-ted member on said machine, adjusting means connected to said slot-ted member for adjustment thereof into'differentpositions of obliqueness, said slottedrnember receiving said sliding block and said sliding block being slidable in said slotted member transversely of the axis of said lower drive shaft in response to movement of. said eccentric.

dog and operatively connected to said feed bar drive shaft, an eccentric bar pivotally connected at one end to said feed bar drive ,7 shaft and having two eccentric engaging .jaws at the other end, an eccentric member mounted on thefree end of said lower drive'shaft, said eccentric bar having a bridge "member intermediate said two jaws, said bridge, member having a stud extending substantially coaXially with the axis of said lower drive shaft and a slidingblock rotatably mounted on said stud,

and a slotted memberrmeans rota tably mounting said slotted member'on said :machine, adjusting means conriected to said slotted member for adjustmentthereof into different positions of obliqueness, said slotted member receiving saidsliding block and sai d sliding block being slidable in said slotted member transversely of the axis of said lower drive shafitin response to movement ofsaid' eccentric with said lower drive shaft to effect adjustment of said drive means, said machine having a base and a standard a secondv stud fixedly mounted in said base of the -machine rotatably supporting saidslotted member and a control disk having a slot therein, said disk being rotatably supported in said standard of said machine, and

" said adjusting means including a double armed lever hav- 7 ing' one arm in engagement'with said disc slot and another arm linked to said slidingblock.

I References Cited by the Examiner V UNITED STATES PATENTS JORDAN: FRANKLIN, Primary Examiner. 

1. A SEWING MACHINE OF THE TYPE HAVING A FEED DOG, A FEED BAR SHAFT AND A LOWER DRIVE SHAFT FOR DRIVING THE LOOPER AND DRIVE MEANS CONNECTED BETWEEN SAID DRIVE SHAFTS FOR EFFECTING MEANS CONNECTED BETWEEN SAID DRIVE DOG, SAID DRIVE MEANS INCLUDING A FEED BAR SUPPORTING SAID FEED DOG AND OPERATIVELY CONNECTED TO SAID FEED BAR DRIVE SHAFT, AN ECCENTRIC BAR PIVOTALLY CONNECTED AT ONE END TO SAID FEED BAR DRIVE SHAFT AND HAVING TWO ECCENTRIC ENGAGING JAWS AT THE OTHER END, AN ECCENTRIC MEMBER MOUNTED ON THE FREE END OF SAID LOWER DRIVE SHAFT, SAID ECCENTRIC BAR HAVING A BRIDGE MEMBER INTERMEDIATE SAID TWO JAWS, SAID BRIDGE MEMBER HAVING A STUD EXTENDING SUBSTANTIALLY COAXIALLY WITH THE AXIS OF SAID LOWER DRIVE SHAFT AND A SLIDING BLOCK ROTATABLY MOUNTED ON SAID STUD, AND A SLOTTED MEMBER MEANS ROTATABLY MOUNTING SAID SLOTTED MEMBER ON SAID MACHINE, ADJUSTING MEANS CONNECTED TO SAID SLOTTED MEMBER FOR ADJUSTMENT THEREOF INTO DIFFERENT POSITIONS OF OBLIQUENESS, SAID SLOTTED MEMBER RECEIVING 